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  • 1
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 34 (1988), S. 1-8 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Results of a computer study are reported applying data reconciliation and interpretation techniques to a single-stage flash operation. Measured errors in the process variables are significantly reduced. The techniques are successfully extended to estimate flash efficiency. The flash efficiency is estimated using two methods: (1) a statistically rigorous simultaneous data reconciliation and efficiency estimation procedure, and (2), a faster, nonrigorous sequential procedure. It is found that the simultaneous procedure provides better measured variable and flash efficiency estimates.
    Additional Material: 8 Ill.
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  • 2
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 34 (1988), S. 37-44 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Steady states with different flow rates and temperature profiles may exist in a monolith or multitube packed-bed reactor operating under a prescribed pressure drop, due to the coupling among the species, energy, and momentum balances, and the change of physical properties with temperature and pressure. Criteria are derived predicting the conditions under which thermoflow multiplicity can occur for a gaseous reaction involving a change in the number of moles. In general, a reaction-induced volume increase enables thermoflow multiplicity to occur for reactions with a lower adiabatic temperature rise. A surprising finding is that thermoflow multiplicity may be found for an isothermal reaction involving a volume decrease. This point emphasizes the difference in the feedback mechanism leading to thermoflow and thermokinetic multiplicity.
    Additional Material: 8 Ill.
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  • 3
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 34 (1988), S. 123-129 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A light-extinction principle was used to measure the fall speeds of the interfaces that develop during gravity sedimentation of monodisperse, bidisperse, and tridisperse suspensions of noncolloidal particles with small particle Reynolds numbers in the semidilute total particle volume fraction range 0.0003 ≤ c0 ≤ 0.15. For monodisperse suspensions, the hindered settling velocity of the interface at the top of the suspension was found to be well represented by the correlation of Richardson and Zaki, provided that the isolated particle fall speed was chosen by linear extrapolation of the data to c0 = 0, with 90% confidence intervals on the exponent of n = 5.0 ± 0.1. For dilute monodisperse, bidisperse, and tridisperse suspensions, the hindered settling velocities of the interfaces showed agreement within experimental uncertainty with the theory of Batchelor, which predicts that the settling velocity decreases linearly with increasing particle concentration and which is based upon pairwise particle interactions.
    Additional Material: 6 Ill.
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  • 4
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 34 (1988), S. 144-146 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 4 Ill.
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  • 5
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 34 (1988), S. 158-162 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 3 Ill.
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  • 6
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 34 (1988), S. 209-222 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A model is presented for convection and chemical reacton in porous media. An irreversible chemical reaction of arbitrary order is considered. Reactant depletion allows for basic solutions in either the kinetic or the diffusion regime. The cases of forced flow parallel to the lateral walls of the cavity and a closed system are addressed. A linear stability analysis of the basic states is performed and critical values of the thermal Rayleigh number for the onset of natural convection are determined. A dispersion relation is derived and a graphical representation of the linear stability analysis results is provided for typical values of the system parameters. Analytical predictions are verified by results obtained by numerical integration of the complete set of nonlinear partial differential equations. The effect of natural convection is discussed when the basic state is either in the kinetic or in the diffusion regime. For large gradients, associated with the diffusion regime, chemical reaction can drive free convection even for low values of the Rayleigh number. In forced flow systems, natural convection can change substantially the flow pattern of the system.
    Additional Material: 12 Ill.
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  • 7
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 34 (1988), S. 253-262 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Aerosol deposition in model filters composed of layers of parallel fibers with the orientation of the fiber of each layer kept arbitrary was simulated stochastically. Particle positions at the inlet of the filter were assumed to be randomly distributed over the inlet plane with the trajectory assumed to be rectilinear because of the particles' high inertia. In the simulation, the track of each particle through the filter was monitored and the possible bounce-off from collision surfaces was allowed for. Deposition behavior and the structure of deposits were studied with various aerosol flow conditions and filter characteristics.
    Additional Material: 19 Ill.
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  • 8
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 34 (1988), S. 45-54 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A theoretical and experimental study on the dissolution of porous media by flowing acid has been carried out. Dissolution of the media results in an evolution of the pore geometry and the formation of random flow channels. The goal is to predict the range of conditions under which channels will form, and the effects of various parameters on the structure of the channels and on their rate of propagation through the media. A random network model is used to describe the behavior of the stochastic, rootlike channels that form during flow and dissolution in carbonate rock and in other systems. The structure of the flow channels that form as a result of acid attack are characterized and studied using a Wood's metal casting technique. A comparison of model results shows that the rates of channel formation and growth are intimately related to the developing structure of the channels (size of branches and degree of branching), which in turn is controlled by factors such as the fluid velocity and the rate of reaction. Depending on the experimental conditions, the channels range from a single conduit with a minimum of branching to a highly branched, spongy network of channels. The dependence of permeability increase and channel branchedness on injection rates and acid diffusion rates is described by the Damkohler number for flow and reaction.
    Additional Material: 18 Ill.
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  • 9
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 34 (1988), S. 329-332 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 3 Ill.
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  • 10
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 34 (1988), S. 341-346 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 4 Ill.
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  • 11
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 34 (1988), S. 353-365 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Spontaneous combustion may occur in a coal stockpile when the heat generated within the pile cannot be dissipated at near ambient temperature. Under practical conditions, natural convection enhances the rate of heat removal from the bed and shifts the ignition to lower particle sizes (higher reactivities). Analysis of three limiting cases of a one-dimensional model yields criteria predicting the conditions under which ignition occurs as well as those for which a low-temperature (extinguished) state exists for all particle sizes. A simple asymptotic relation predicts the ignition point at large Rayleigh numbers.
    Additional Material: 14 Ill.
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  • 12
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 34 (1988), S. 499-501 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 3 Ill.
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  • 13
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 34 (1988), S. 514-518 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 3 Ill.
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  • 14
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 34 (1988), S. 55-68 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Mass transfer coefficients for the solution, without reaction, of oxygen in cyclohexane over a wide range of temperature and pressure have been measured in a flat interface reactor (FIR) and a gas sparged stirred-tank reactor (STR). Solubilities have also been measured and it is suggested that a modified Henry's law coefficient of 1.09 × 10-2 kmol/m3 · bar can be regarded as constant over the temperature range 293-435 K. The physical mass transfer coefficient in the STR shows very little variation over this temperature range and a value of 3.5 × 10-4 m/s can be assumed for 423-435 K. However, coefficients in the FIR increase with agitation rate as expected. The difference is ascribed to interference by neighboring bubbles in the transfer process, when diffusivities are high, and also to the lowering of surface tension at high temperatures. A model proposed by Gal-Or and Resnick is reviewed in its application to the present system.
    Additional Material: 11 Ill.
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  • 15
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 34 (1988), S. 335-340 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 5 Ill.
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  • 16
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 34 (1988) 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
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  • 17
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 34 (1988), S. 389-396 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The structure of the wavy interface on a falling liquid film is studied for conditions of countercurrent gas flow in order to investigate mechanisms for flooding. Measurements taken just below the liquid feed and at 1.7 m down the tube show that under all conditions, including flooding, the waves propagate only downward and are never of such amplitude as to bridge the tube. These observations are in contrast to speculations in the literature that upward flow of waves or bridging of liquid due to waves cause flooding. In the mechanism suggested, flooding is due to flow reversal in the film just at the liquid entry.
    Additional Material: 15 Ill.
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  • 18
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 34 (1988), S. 150-154 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 5 Ill.
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  • 19
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 34 (1988), S. 167-170 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 6 Ill.
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  • 20
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 34 (1988), S. 170-170 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
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  • 21
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
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  • 22
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 34 (1988), S. 189-194 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Micellar-enhanced ultrafiltration can be used to remove multivalent anions or cations from aqueous streams. In the removal of chromate ions (CrO42-), the cationic surfactant hexadecylpyridinium chloride is added to the solution, and the chromate ions preferentially adsorb at the surface of the highly charged surfactant micelles. The solution is processed by ultrafiltration, using a membrane with pore sizes small enough to block the passage of the micelles and adsorbed ions. The permeate solution has a chromate concentration less than 0.1% that in the original stream. A new equilibrium model, combining the simple two-phase polyelectrolyte theory of Oosawa with thermodynamic activity, material-balance, and charge-balance equations, successfully correlates ultrafiltration and equilibrium dialysis results for chromate solutions.
    Additional Material: 1 Ill.
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  • 23
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 34 (1988), S. 705-722 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Enhancement of simultaneous heat and mass transfer due to surface tension gradient-induced Marangoni convection is studied. The geometry considered is a thin liquid film between a solid phase and a gas phase. In regions where the two Marangoni numbers are of opposite signs (quadrants II and IV), Orr-Sommerfeld analysis reveals the possibility of oscillatory roll cells. A nonlinear bifurcation study of the amplitude equations indicates that the finite-amplitude oscillatory rolls are annihilated by steady rolls slightly beyond the oscillatory stability boundary in a heteroclinic bifurcation. Oscillatory rolls are hence restricted to quadrants II and IV. Finite-amplitude instability due to subcritical bifurcation of the steady rolls is also shown to be limited to these quadrants. In addition to classifying the bifurcations, the numerical study also provides a useful correlation for single-component flux enhancement, Nh* = 1 + 0.001324 Nu0.23Pr0.16(NT - NTc), which is compared to available experimental data.
    Additional Material: 14 Ill.
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  • 24
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 34 (1988), S. 529-540 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Large favorable pressure gradients can cause the drag of a turbulent boundary layer on a solid surface to decrease; if large enough, such gradients can cause a return to laminar flow. Scaling relations and a computational model for the viscous wall layer, recently developed in this laboratory are used to interpret this phenomenon.
    Additional Material: 14 Ill.
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  • 25
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 34 (1988), S. 574-582 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Fossil fuel process oils consist of such a large number of components that their only proper description is in terms of continuous distribution functions of a suitable characteristic variable. A methodology is presented to describe the oils in terms of a generalized distribution function. The characteristic variable is determined from measurements of the equilibrium ratios of two test oils, at ambient pressure. Application of the proposed methodology to a sequence of operations shows that, unlike the pseudocomponents technique, the level of accuracy can be maintained.
    Additional Material: 10 Ill.
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  • 26
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 34 (1988), S. 314-320 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: An a priori model is developed to assess the heat effects during gas-phase (H2S/H2) sulfiding of a CoO—MoO3/γ—Al2O3 hydroprocessing catalyst in a small fixed-bed reactor. The model satisfactorily predicts the observed maximum temperature rise and the speed of the traveling exotherm. It is found that the amount of heat released can be of sufficient magnitude to cause significant hot spotting and local starvation of H2S, both of which need to be avoided for desired catalyst performance. With this model, parametric studies were made to optimize the sulfiding operation. It is expected that the model can be used to guide catalyst synthesis research and to scale up laboratory/pilot-plant sulfiding procedures.
    Additional Material: 12 Ill.
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  • 27
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 34 (1988), S. 333-334 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 2 Ill.
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  • 28
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 34 (1988), S. 626-632 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: On-line optimizing control has been used to find and track the economically optimal operating conditions of a packed-bed reactor. The continuous reactor under study converts the ammonium salt of fumaric acid to aspartic acid using whole cells immobilizing in K-carrageenan beads. The on-line optimizing control was performed using a leastsquares recursive estimation algorithm with a variable forgetting factor to estimate the parameters in a linear discrete-time model. A Newton optimization procedure used these parameters to calculate the direction and distance to the optimal conditions. Features found to enhance the speed and stability of the algorithm included the use of a variable forgetting factor algorithm, both low- and high-pass filtering of the data, outlier rejection, and linearizing input-outupt transformations.
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  • 29
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    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 34 (1988), S. 669-671 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 2 Ill.
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  • 30
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    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 34 (1988), S. 684-687 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 6 Ill.
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  • 31
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    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 34 (1988), S. 698-701 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 4 Ill.
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  • 32
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    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 34 (1988), S. 474-482 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Recycle continuous-flow electrophoresis (RCFE) is a modification of Hannig's thin-film CFE device in which eluant is continuously recycled to the chamber inlet. Shifting the recycled eluent laterally a specific distance prior to reinjection enables the RCFE to separate any two solutes to arbitrary purity. This paper studies solute transport in an idealized RCFE in the absence of diffusion. The model is solved analytically by means of a two-sided Laplace transform. Three distinct types of solute distribution are found, and guidelines for construction and operation of an RCFE are derived.
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  • 33
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    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 34 (1988), S. 506-509 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 5 Ill.
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  • 34
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    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 34 (1988), S. 519-523 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 8 Ill.
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  • 35
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    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 34 (1988), S. 525-526 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
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  • 36
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    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 34 (1988), S. 1106-1118 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Diffusion flux models are developed for isobaric diffusion of a multicomponent gas mixture in pore networks of distributed pore size and length constructed by arranging pore segments around the bonds of a lattice of constant coordination number. Eigenvalue-eigevector analysis is used to decompose the dusty-gas model equations, written for each pore segment in the network, into a set of independent single-species diffusion problems, each of which is then treated by combining the effective medium theory for resistor networks with the smooth field approximation (Burganos and Sotirchos, 1987). Results for a ternary mixture diffusing in a porous slab show that direct application of the smooth field approximation underestimates significantly the mass transport resistance.
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  • 37
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    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 34 (1988), S. 849-852 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 6 Ill.
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  • 38
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    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 34 (1988), S. 870-872 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 2 Ill.
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  • 39
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    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 34 (1988) 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
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  • 40
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    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 34 (1988), S. 1185-1189 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Nuclear magnetic resonance (NMR) tracer desorption technique in combination with the traditional pulsed field gradient technique is applied to measure directly intracrystalline and long-range molecular transport, as well as molecular exchange rates, between the individual crystallites in granulated molecular sieves. It is found that the granulation process leads to the formation of transport resistances on the external surface of the crystallites, which may be dramatically enhanced during their technical application. As an example, for granulated zeolite NaCaA the enhancement of such surface barriers under hydrothermal conditions and under the influence of a hydrocarbon atmosphere is studied. Since both intra- and intercrystalline transport are found to remain practically unaffected by this treatment, changes in the overall transport behavior are caused by the enhanced transport resistance on the external surface of the zeolite crystallites.
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  • 41
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    AIChE Journal 34 (1988), S. 790-802 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A model for the rapid devolatilization of individual coal particles is developed by analogy with a single-stage equilibrium flash distillation. In the theory, thermal depolymerization of the coal generates aromatic fragments that are widely distributed in size. Conditions for phase equilibrium determine the partitioning of these fragments into intermediates in the condensed phase, which ultimately form char and light gas, and into tar vapor, which escapes in a stream of light gases. Comparison with data shows that the model accurately correlates the yields of noncondensible gas and tar from bituminous coals over wide ranges of temperature and pressure. The predicted molecular weight distributions of tar are also in agreement with measured distributions, and the model yields a mechanistic basis for their observed insensitivity to temperature. The tendency to form lighter tar at higher pressures is also explained.
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  • 42
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    AIChE Journal 34 (1988), S. 1225-1228 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 6 Ill.
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  • 43
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    AIChE Journal 34 (1988), S. 1249-1256 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The production of powders by aerosol routes spans a wide range of operating temperatures depending on the type of aerosol reactors used. The dominant mechanism of particle growth and evolution depends highly on the rate at which the reactions producing the condensible species are carried out. Numerical solutions of the discrete-sectional aerosol general dynamic equation that accounts for the interactions of the discrete clusters were obtained for conditions representative of the different types of aerosol reactors used for powder production today. Simplified reaction and coagulation equations that give fast and useful prediction of the evolution of aerosols associated with chemical reactions were derived, and a simple reaction-coagulation model was developed. The effects of reaction rate, initial vapor concentration, residence time, seed particles, and temperature profile on the properties of tine particles produced by gas-phase chemical reactions were evaluated using both models. Results show good agreement between the two.
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  • 44
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    AIChE Journal 34 (1988), S. 1299-1309 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Lumping of the kinetics of mixtures described by a continuous distribution function of concentration is discussed for the case where individual reactions have nonlinear kinetics. The assumption of independent kinetics, which leads to a paradox, is not used. Functional-differential equations govern the kinetic behavior of the mixture. Formal solutions are presented for a class of kinetic behavior that includes Langmuir isotherm catalysis and for the special case of bimolecular reactions. A class is defined for which the kinetic functionals can be expanded in a series of integrals for which the kernels are entirely determined. Finally, a thermodynamic analysis is presented to show that the commonly accepted equilibrium theory implies a kinetic approximation of maximal rank for the kinetics at the equilibrium point.
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  • 45
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    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 34 (1988), S. 825-833 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The pressure of water is decoupled into a polar pressure and a nonpolar pressure, the latter being obtained from the BACK equation based on the size and nonpolar energy of the water molecule determined by Jorgensen and coworkers. The polar pressure is obtained upon subtracting the nonpolar pressure from the total pressure given by the steam table equation of Keenan et al. The polar pressure function thus obtained for water is generalized to augment the BACK equation for the general description of polar fluids.Equation constants are reported for 26 substances. Calculated vapor pressure, liquid molal volume, and pressure-volume-temperature (PVT) behavior are compared with data. Mixing rules are introduced to express poles interacting with poles and dispersion modes interacting with dispersion modes, but not poles interacting with dispersion modes. PVT relationship, vapor-liquid equilibrium, and liquid-liquid equilibrium in mixtures of water and nonpolar substances are calculated.
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  • 46
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    AIChE Journal 34 (1988), S. 865-869 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 6 Ill.
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  • 47
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    AIChE Journal 34 (1988), S. 881-911 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The quality of large semiconductor crystals grown from the melt for use in electronic and optoelectronic devices is strongly influenced by the intricate coupling of heat and mass transfer and melt flow in growth systems. This paper reviews the present state of understanding of these processes starting from the simplest descriptions of solidification processes to detailed numerical calculations needed for quantitative modeling of processing with solidification. Descriptions of models for the vertical Bridgman-Stockbarger and Czochralski crystal growth techniques are included as examples of the level of understanding of industrially important methods.
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  • 48
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    AIChE Journal 34 (1988), S. 938-945 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Coherent flow-oriented structures, with a dimensionless spacing of λ+ ≈ 100, observed close to a wall in turbulent flows are believed to control the production of turbulence. A 2 1/2 D computer model developed by Nikolaides is used to explain the dimensionless spacing of these structures. The calculations suggest that the net production of turbulence in the viscous wall region is sensitive to changes in λ+ in the neighborhood of λ+ ≈ 100. They indicate that the net production is negative for λ+ 〈 85 and that for λ+ = 93 the net production is large enough to supply the turbulent energy dissipated in the outer flow.
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  • 49
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    AIChE Journal 34 (1988), S. 969-979 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The partial internal wetting of spherical catalyst particles exposed to saturated vapor is investigated here by considering the interplay of capillary condensation phenomena and thermal effects for a first-order irreversible reaction. It is shown that for certain very narrow ranges of parameters steady states can exist in which the macropores are vapor-filled while micropores in an inner core, or an outer shell, are liquid-filled. Under certain conditions even two such steady states are found, although only one of them can be stable. In addition to these there exist states in which all the micropores are liquid-filled or those in which the entire particle is internally dry.
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  • 50
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    AIChE Journal 34 (1988), S. 1020-1026 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Ion exchange accompanied by a neutralization reaction has been analyzed for the general cases where the bulk solution contains a neutral salt and an acid or a base, e.g., [R · H] + (NaCl + NaOH). Both intraparticle and liquid film diffusion are considered. The Nernst-Planck equation was applied for the fluxes of the ionic species in the liquid film and the resin phase with a mobile reaction plane in the liquid film. When the solution contains acid or base more than 50%, the exchange rate is approximated by the case for pure acid or base solution: the reaction plane is located at the solid/liquid interface. When the solution contains acid or base less than 50% (this situation is generally encountered in the case where a neutral salt flows through a mixed bed of OH-form and H-form resins), the mobile reaction plane should be considered. When the ratio of intraparticle diffusion resistance to liquid diffusion resistance defined in the text is larger than 2, the exchange rate can be approximated by intraparticle diffusion control. The larger the ratio, the faster the reaction plane moves to the resin particle surface. Experimental uptake curves for the ion exchange systems [R · H] + (NaCl + NaOH) and [R · OH] + (NaCl + HCl) confirm the above conclusions.
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  • 51
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    AIChE Journal 34 (1988), S. 1407-1407 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
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  • 52
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    AIChE Journal 34 (1988), S. 1577-1580 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
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  • 53
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    AIChE Journal 34 (1988), S. 1595-1606 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: To obtain good representation in the liquid-liquid critical region, a semitheoretical correction is added to a conventional expression (e.g., van Laar or NRTL) for the excess Gibbs energy of a binary or ternary system along the coexistence curve. This correction is an exponential function of a suitable distance from the critical point; it is significant in the critical region but not elsewhere. In the correction function, the preexponential factor is determined from stability considerations. In the exponential argument, two parameters are determined from theoretical power laws. While the coordinates of the critical point must be known (or estimated), no phase-equilibrium data in the critical region are required to determine parameters. The correction presented here provides an excellent approximation for phase equilibria along the coexistence curve close to and remote from critical conditions. Further, the correction facilitates simultaneous representation of isothermal vapor-liquid and liquid-liquid equilibria including the liquid-liquid critical region.
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  • 54
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    AIChE Journal 34 (1988), S. 1634-1648 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Rigorous analytical methods for consistent modeling of control structures for multivariable processes are presented. The continuous distillation process is used to illustrate the methods, but the basic ideas, and more specifically the transformations and consistency relations derived, are valid in general.If steady-state operating data and the process gains of an arbitrary control structure are known, it is possible to calculate the process gains of any feasible control structure. A general expression relating the process gaisn of different control structures is derived. In general, the process gains must also satisfy certain consistency relationships which can be derived from first principles, e.g., steady-state material balances.The usefulness of the results is illustrated by control structure transformations and reconciliation of process gains, by an application to process dynamics, by synthesis of noninteracting control loops, and by derivation of analytical relationships useful in relative gain analysis.
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  • 55
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    AIChE Journal 34 (1988), S. 1673-1682 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The planar-flow melt-spinning process which is used to rapidly solidify metals from the molten state is shown to be dominated by the fluid mechanics of the “puddle” region even though heat-transfer limits the overall thickness of the metal ribbon product. The process is modeled to account for the hydrodynamical forces in the molten region with the influence of heat-transfer entering through a parameter measuring solidification rate relative to wheel speed. It is shown that this parameter H controls the deviation of the flow behavior from classical coating flow solutions; these solutions are recovered in a limiting case of low solidification rate. A perturbation solution in H distinguishes the melt spinning from the coating process and yields the ribbon thickness as a function of wheel-speed and the other process parameters for a class of contact-line conditions. Most interesting of these predictions is the result that under certain conditions there is a window of wheel-speeds for which there is no steady solution. The relationship of predictions with the limited available data from experiment is briefly discussed.
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  • 56
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    AIChE Journal 34 (1988), S. 1698-1708 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The hollow fiber contained liquid membrane (CLM) is a thin liquid film contained in the interstices of two sets of intermingled microporous hollow fine fibers. Organic CLM-s have been used here for the separation of solutes from an aqueous feed into an aqueous strip. Solutes studied are phenol and acetic acid. The separations are carried out in either hydrophilic or hydrophobic hollow fiber CLM permeator modules, using a variety of organic liquids (e.g., decanol, methyl isobutyl ketone, xylene) as membranes. First-order models have been developed to predict the overall solute transfer coefficients adequately. The transfer coefficient can be enhanced significantly when a chemical reaction is carried out on the strip side using NaOH. The advantages of the CLM structure include operational stability, independent control of membrane phase pressure, automatic replenishment of the lost membrane liquid, and absence of the need for preequilibration. These features are demonstrated here, even for systems with considerable aqueous-organic mutual solubilities.
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  • 57
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    AIChE Journal 34 (1988), S. 1135-1145 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A new liquid membrane separation technique for gas mixtures has been developed: feed and sweep gases flow through the lumen of two different sets of hydrophobic microporous hollow fibers while a liquid on the shell side acts as the membrane. This membrane is identified as the contained liquid membrane (CLM). Major shortcomings of immobilized liquid membrane techniques are eliminated. The novel separation device is identified as the hollow fiber contained liquid membrane (HFCLM) permeator. Experimental studies are made with different CO2-N2 feed mixtures and a pure helium sweep stream, with special emphasis on model landfill gas purification. Either pure water or an aqueous solution of K2CO3 is used as membrane. The effects of several variables on the performance of the HFCLM permeator have been studied. A three-component permeation model, incorporating axial pressure drop, is developed for binary mixture separation in a HFCLM permeator having a sweep gas stream. The experimental data show good agreement with the theoretical predictions.
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  • 58
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    AIChE Journal 34 (1988), S. 1789-1802 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Mass transfer in sheared, concurrent gas-liquid flows is investigated theoretically using solutions to the unaveraged advection-diffusion equation. For sufficiently thick films, the resistance to mass transfer is shown to be confined completely within a thin region in the liquid near the interface and mass transfer coefficients are accurately predicted by an improved numerical technique that uses a velocity field derived from an Orr-Sommerfeld equation with the time-varying velocity computed directly from measurements of interfacial waves. The mass transfer coefficients are shown to depend on the magnitude and frequency content of the velocity fluctuations normal to the interface. As the film thickness decreases, transfer resistance extends throughout the film and turbulent mixing in the middle of the film controls the transfer rates. For this region, limiting values of transfer coefficients are predicted well by analytical solutions to the advection-diffusion equation, which assume a laminar flow.
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  • 59
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    AIChE Journal 34 (1988), S. 1229-1232 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
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  • 60
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    AIChE Journal 34 (1988), S. 1257-1266 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Expressions suitable for the description of the behavior of small biological zwitterions in aqueous systems are developed. The validity and usefulness of the expressions are tested by correlating data for the activity coefficients of several amino acids in water. Development of rational expressions for the solid-liquid equilibria (SLE) of amino acids, in terms of the heat of solution at infinite dilution, is also presented. The solubility data of phenylalanine, tyrosine and diiodotyrosine as a function of pH are successfully correlated using the approach developed here. In addition, simultaneous correlation of the pH and temperature dependence of solubility data for diodotyrosine in water gives very good representation. The expressions described here should prove useful for the design and optimization of separation processes, such as crystallization, with minimal experimental information.
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    AIChE Journal 34 (1988), S. 1287-1298 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The performance of Dynamic Matrix Control (DMC) for different product purity distillation columns is studied and compared with a conventional multiloop proportional-integral control structure (LV). The load-rejection capability (regulatory response) of DMC becomes worse than that of the conventional structure as product purity increases. Large load disturbances take the highly nonlinear system away from the nominal linear model, adversely affecting the performance of DMC. The LV structure is less sensitive to process nonlinearities. However, simple nonlinear output transformations suggested by the fundamental design equations of the process give models that are quite insensitive to nonlinearities of the process. This results in a nonlinear version of DMC that has better performance than the standard DMC and it is much simpler than the gain and time constant scheduling DMC or adaptive DMC. The complexity of DMC when it is applied on systems with very large time constants is also addressed. Suggestions to overcome this problem are proposed.
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    AIChE Journal 34 (1988), S. 1341-1353 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A filtering technique is proposed for on-line estimation of the temperature, monomer conversion, initiator conversion, and the entire molecular weight distribution in a batch methyl methacrylate polymerization reactor. The technique uses a detailed polymerization model combined with on-line measurements of conversion, temperature, and the molecular weight distribution, taken at different discrete time intervals. The polymerization model includes a chain-length-dependent termination rate constant which allows the prediction of the molecular weight distribution for common free-radical polymerization conditions. Comparisons between modeling and experimental results show that the polymerization model gives good predictions of the monomer conversion and the molecular weight distribution in the polymerization system. The performance of the estimation scheme is tested for cases of strong gel effect conditions leading to a bimodal molecular weight distribution, and poor initial conditions. Finally, off-line experimental data are used to test the algorithm under actual reactor operating conditions.
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    AIChE Journal 34 (1988), S. 1373-1375 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 2 Ill.
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    AIChE Journal 34 (1988), S. 1387-1391 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
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    AIChE Journal 34 (1988), S. 1403-1406 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
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  • 66
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    AIChE Journal 34 (1988), S. 2069-2072 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 4 Ill.
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  • 67
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    AIChE Journal 34 (1988), S. 1943-1948 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Number of passage distribution (NPD) functions in batch and continuous recirculating systems are presented, and their application to dispersive mixing of plastics and rubber is discussed. Dispersive mixing requires a process of repeated ruptures of the dispersed phase. This is accomplished by repeated passages in special regions of the system where stress levels above a given threshhold value are imposed on the liquid. The application of NPD functions to certain batch and continuous mixers and compounders is discussed.
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  • 68
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    AIChE Journal 34 (1988), S. 1973-1980 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Partial molar properties at infinite dilution for binary Lennard-Jones mixtures are calculated using Monte Carlo simulation methods. The variation of these properties with density, temperature, and intermolecular force parameters is systematically studied. Simulation pair correlation functions are used to examine the structure of the mixtures at the molecular level. Results are also compared to predictions of the van der Waals I conformal solution theory.Partial molar volume and internal energy are found to be strongly dependent on the isothermal compressibility of the mixture and on the proximity of the mixture state condition to phase boundaries. The van der Waals I conformal solution theory gave good results for the infinite-dilution chemical potential μ1∞ and reasonable results for the partial molar internal energies and volumes. However, it is suspected that this is limited to the infinite-dilution case, where the isothermal compressibility of the mixture is well represented by the pure-fluid equation of state.
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    AIChE Journal 34 (1988), S. 2012-2018 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The kinetics of dissolution of alumina in aqueous solutions of H2SO4 was studied at ambient temperature under continuous-flow conditions. The results are consistent with a model involving rapid hydration of the surface, adsorption-desorption of H+ to form precursor sites, and rate-determining parallel reactions of the precursor sites to form dissolved aluminum and an insoluble surface species. The model also involves renewal of a precursor site after each dissolution step.The adsorption-desorption of H+ was represented by a Langmuir isotherm. The dissolution data were correlated by a kinetic equation that was developed by assuming the dissolution step is first order in precursor concentration, and the deactivation step is second order in precursor concentration.
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    AIChE Journal 34 (1988), S. 2059-2062 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 6 Ill.
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    AIChE Journal 34 (1988), S. 2073-2076 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
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    AIChE Journal 34 (1988), S. 1511-1518 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Thin polymeric films have been applied to the surface of a porous material in a novel process. Nitrogen sorption, a conventional tool for measuring surface areas and pore size distributions, can be employed for determining the thickness of such films through a comparison of the pore size distribution curves before and after film formation. The thickness of a polystyrene film on a porous alumina powder is determined and compared with the theoretical thickness for styrene polymerized inside a two-dimensional solvent, which consists of a partial bilayer of sodium dodecyl sulfate physically adsorbed from an aqueous solution onto the powder. Film thicknesses ranged from 1.8 to 0.4 nm while BET surface area decreased from 94.7 to 57.8 m2/g. The powder surface changes from hydrophilic to hydrophobic while retaining the basic pore structure.
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    AIChE Journal 34 (1988), S. 1568-1572 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 9 Ill.
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  • 74
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    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 34 (1988) 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
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  • 75
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    AIChE Journal 34 (1988), S. 1656-1662 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Pyrolysis and regeneration kinetics of 11 spent activated carbons were studied using a thermal balance and a fludized bed reactor. The adsorbates were aromatic compounds with different types and number of side groups, and most of the side groups were lost on pyrolysis, leaving a residue about equal to the weight of the aromatic portion of the adsorbate. The residues from alkyl phenols reacted with oxygen at 770-920 K at rates up to 12 times the rate for the base carbon. There was a similar increase in oxygen chemisorption indicating increased number of active sites. The adsorption capacity of the carbons was mostly recovered by pyrolysis, even though the surface area and pore volume were reduced by the residue. Some oxidative regeneration is probably necessary to restore adsorption capacity for repeated use.
    Additional Material: 15 Ill.
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  • 76
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    AIChE Journal 34 (1988), S. 1691-1697 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The effect of suspended activated carbon on gas/liquid mass transfer is studied for the Pd/C-catalyzed hydrogenation of nitrate to hydroxylamine (HPO process). In a bubble column and in a stirred autoclave, physical mass transfer (kLa) in the concentrated salt solution is improved by more than a factor of three by the catalyst. Chemical absorption enhancement by the zero-order catalytic reaction is insignificant at the employed catalyst diameter (40 μm), but hydroxylamine selectivity depends on the absorption regime.
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  • 77
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    AIChE Journal 34 (1988), S. 1718-1721 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 4 Ill.
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  • 78
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    AIChE Journal 34 (1988), S. 1773-1780 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The augmented BACK equation of state for polar fluids is extended to mixtures by introducing mixing rules separately for the nonpolar and polar interactions. Fluid phase equilibria are calculated for polar + nonpolar, and polar + polar mixtures including mixtures of hydrogen-bonding substances. Enthalpy calculations are illustrated with enthalpy of H2S + N2 and heats of mixing of steam mixtures, and carbon dioxide mixtures.Cross interaction coefficients are adjusted for the correlation of data on binary mixtures. Both phase equilibrium and enthalpy data are correlated at the same time with two such coefficients for each binary. The cross interaction coefficients are constants, invariant with temperature, density, or phase state.
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  • 79
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    AIChE Journal 34 (1988), S. 1949-1958 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Alternating current impedance measurements can be used as an in situ method for characterizing rate-limiting processes in fuel cell electrodes. Theoretical models have been derived and solved analytically. Theoretical analysis indicates that kinetic information can be extracted from the effect of temperature and gas composition on the size of the kinetic loop. The relative importance of kinetics and mass transfer can be inferred from AC impedance analysis. Several examples are given for the case of molten carbonate fuel cell (MCFC) electrodes. Such electrodes are not accessible to classical kinetic investigation techniques due to the high operating temperature and corrosive environment. Relevant kinetic information about MCFC electrodes has been obtained successfully using this in situ technique.
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  • 80
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    AIChE Journal 34 (1988), S. 1996-2004 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The ways in which modeling uncertainties are described for a particular process critically affects the results obtained in robustness studies. In this paper, four multivariable robust stability methodologies are used to characterize and analyze the effects of model inaccuracy due to non-linearity in high-purity distillation processes. The unstructured and structured singular value, numerical range, and a mapping of det(l + GPGc) are compared in terms of their ability to predict the stability of the dual-composition control system over a wide composition range. The importance of using uncertainty descriptions that include a realistic representation of the phase-magnitude relationship as well as the corrections between uncertainties in each element of the model is demonstrated. The conservation associated with norm-bounded uncertainty descriptions reveals itself by the extent of detuning needed to insure stability and the subsequent degradation in control performance.
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  • 81
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    AIChE Journal 34 (1988), S. 2030-2040 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Discrete models are developed to simulate the reaction of solids with complex pore structures in the kinetic- and diffusion-controlled regimes. Simulations employ two- and three-dimensional computational grids, and model parameters are directly obtainable from measurable physical properties of the unreacted solid. Model predictions can be displayed pictorially, allowing for direct visualization of the simulated process, while image processing of the computational grids can provide detailed structural information not easily obtainable from other analytical models. The effects of various pore structural parameters on the predicted reactivity patterns are investigated. Several examples are presented to illustrate the use of the models and demonstrate the significance of the pore structure in determining the reactivity of coal-derived chars.
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    AIChE Journal 34 (1988), S. 2063-2068 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 9 Ill.
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  • 83
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    AIChE Journal 34 (1988), S. 2080-2082 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
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  • 84
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    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 3 Tab.
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  • 85
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    AIChE Journal 34 (1988) 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
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    AIChE Journal 34 (1988), S. 175-175 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
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  • 87
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    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 34 (1988) 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
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  • 88
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    AIChE Journal 34 (1988), S. 293-304 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Experimental and theoretical studies on a backflush hollow-fiber enzymatic reactor (HFER) were conducted in this work for a lactose/lactase system. An A. niger lactase was chosen, from the four lactases tested, for reversible immobilization in the sponge layers of the fibers. An enzyme loading procedure was developed that allowed reliable and reproducible operation of the hollow-fiber reactor and produced industrially significant conversions without apparent change in the activity or stability of the lactase used. This reversible immobilization scheme also permitted easy replacement of the enzyme used. The performance of the backflush HFER was investigated and a large number of data concerning its operation were obtained and interpreted. Momentum and mass transports in such a HFER were analyzed, and mathematical models that took the experimental findings into consideration were also developed and solved analytically and/or numerically. Predictions from the computer model developed in this work were found to be in excellent agreement with the experimental data collected, suggesting the possibility of a priori design of a process-scale backflush HFER. With minor modifications, the models developed are expected to be applicable to hollow-fiber reactors with a wide selection of immobilized cells, organelles, and other enzymes.
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    AIChE Journal 34 (1988), S. 94-106 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Viscoelasticity, nonisothermality, and fountain flow influence the microstructure development during injection mold filling of polymer melts and, therefore, the ultimate properties of a molded article. A comprehensive two-dimensional mathematical model is developed to evaluate the effects of these factors on the structure of the flow field. Special consideration is given to the shape of the flow front, which is crucial in determining the structure of flow in the fountain region. The effects of slip and crystallization are also considered and their influence on model predictions are analyzed. Simulations using the no-slip and slip boundary conditions show that a slip boundary condition is necessary to alleviate the singularities in the flow structure. The results also indicate that the predicted stress profiles are significantly influenced by the viscoelasticity of the polymer melt. Furthermore, the nonisothermality and subsequent deposition of a solid layer next to the mold walls considerably alter the moldability parameters and the flow field.
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  • 90
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    AIChE Journal 34 (1988), S. 130-136 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Differential protein extractions were measured with two types of extractants: inverted micelles and two-phase aqueous systems. The results show that hollow-fiber extractions are substantially faster than those possible in conventional equipment. The extractions are not compromised by loading or flooding because the flows of extractant and raffinate are almost completely independent. Mass transfer coefficients inferred from the measurements both support and extend design equations for these contactors.
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    AIChE Journal 34 (1988), S. 147-149 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
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  • 92
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    AIChE Journal 34 (1988), S. 163-166 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 3 Ill.
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  • 93
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    AIChE Journal 34 (1988), S. 173-173 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
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  • 94
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    AIChE Journal 34 (1988), S. 174-175 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
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  • 95
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    AIChE Journal 34 (1988), S. 177-188 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Extensive studies on dispersion-free solvent extraction have been carried out using modules made with either hydrophobic or hydrophilic microporous hollow-fiber membranes. Membrane and boundary layer resistances have been characterized for both kinds of hollow fiber using solvent extraction systems with a wide variation of distribution coefficients and interfacial tensions. It has been found that the Graetz solution for a constant wall concentration describes satisfactorily mass transfer on the lumen side of a hollow-fiber device. A correlation of the form NSh = [Dh(1 - φ)/L]NRe0.6NSc0.33 appears to provide a close fit to the shell-side mass transfer coefficient data. The perforamnce characteristics of dispersion-free extraction in hollow-fiber modules have been considered against those of commercial packed-bed extractors. A perspective has been provided on comparative utilities of hydrophobic or hydrophilic hollow fibers for a given solvent extraction problem.
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    AIChE Journal 34 (1988), S. 223-228 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The dispersion of emissions from a plume in a cross stream was studied using both experimental and theoretical techniques. Wind tunnel experiments were done for three jet to cross stream velocity ratios: R = 0.5, 1, and 2. The concentration in the plane perpendicular to the cross stream was measured using light scattering and photographic image analysis. The analysis of the negatives revealed the presence of two counterrotating vortices that greatly affected dispersion of smoke in the plume.Convection and random turbulent dispersion were modeled with a statistical convection simulator on a CYBER 205 computer. The input velocities to the convection model were obtained using experimental measurements. The model revealed the effects of the vortices on dispersion, and the concentration distributions across the plume were determined once the vortices had dissipated. The existence of the counterrotating vortices and their effects upon plume dispersion showed that the Gaussian plume model, which is widely used for modeling pollutant dispersion, is inapplicable in the near range of the model stack.
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  • 97
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    AIChE Journal 34 (1988), S. 263-271 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Two models are presented that can simulate two peaks in a temperature-programmed desorption (TPD) spectrum from a high surface area catalyst at atmospheric pressure: a multisite model and a subsurface diffusion model. The multisite model assumes that the two peaks arise from two distinct adsorption sites on the catalyst surface with different activation energies for desorption. The subsurface diffusion model assumes that the high-temperature peak is produced by adsorbate that diffuses into the subsurface region of the catalyst during heating, and then back to the surface when it becomes depleted by the desorption process. It is shown that one can distinguish between the two models experimentally by measuring the effect of carrier gas flow rate and heating rate on the TPD spectrum.
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  • 98
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    AIChE Journal 34 (1988), S. 305-313 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A model is developed to qualitatively predict the effect of a nonuniform activity distribution on the total quantity of metal deposited in hydrodemetallation catalysts. A fixed catalyst support system is assumed and no restrictions are placed on local or overall catalytic activity in seeking an optimal solution that maximizes the amount of contaminant metal deposition over the useful catalyst life. Results indicate that deposition capacity could be substantially increased by a nonuniform activity profile in which the activity at the catalyst center is higher than that at the outer edge. The shape of the optimum activity profile is presented along with practical design improvements.
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    AIChE Journal 34 (1988), S. 326-328 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 3 Ill.
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    AIChE Journal 34 (1988), S. 347-349 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
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